Vacuum packaging apparatus and method



March 24, 1964 R, MAHAFFY ETAL VACU M PACKAGING APPARATUS AND METHOD 3 Sheets-Sheetl E\ .m n F Filed May 5, 1962 March 24, 1964 R. A. MAHAFFY ETAL 3,125,839

VACUUM PACKAGING APPARATUS AND METHOD Filed May a, 1962 s Sheets-Sheet 5 lNvENTORs JohnJi. Harder Mlflwr W ATTO EYS Reid J1. Mahaffy United States Patent Grove, NJ. Filed May 3, 1962, Ser. No. 192,188 19 Claims. (Cl. 533t)) This invention relates to packaging apparatus. More in particular, this invention relates to apparatus for use with flexible packaging material, and to improved methods and means for packaging various products with such material.

In recent years, a number of automatic machines have been developed to produce evacuated or gas-filled thermoformed packages of plastic material such as combinations of polyethylene, Mylar and Saran. One machine of this class having a number of advantageous features is disclosed in copending application Serial No. 842,365, filed on September 25, 1959, by Reid A. Mahaify, now Patent No. 3,061,984, issued November 6, 1962. The machine of that application includes a plurality of separate identical trays mounted on an endless chain which is driven with an intermittent motion past a series of packaging stations where certain operations are performed sequentially to convert thin plastic film into evacuated packages containing products such as luncheon meat, frankfurters, etc. These packaging operations basically comprise the steps of 1) applying a first film of plastic packaging material over the open top of a tray, (2) stretching this plastic material down into the tray by the application of vacuum to the bottom of the tray, (3) depositing the product to be packaged in the tray, (4) applying a second film of plastic packaging material over the top of the tray, (5) partially sealing the two plastic films together while leaving an evacuation opening, (6) evacuating the partiallysealed container through the opening, and (7) completely sealing the two films together to produce an evacuated and hermetically-sealed package with the product therein.

Commercial experience with machines of this class has indicated the need for producing packages having a greater depth than could be obtained with previous procedures. For example, it is desirable to produce packages containing ten frankfurters arranged in two rows of five each (referred to as a five-over-five relationship), weighing about one pound. Heretofore, the methods available have permitted the formation of vacuum packages on a commercial basis to a maximum depth of about 1", so that in a single package it has been possible only to pack five frankfurters in a side-by-side relationship, weighing about one-half pound. Since frankfurters typically are sold in one pound units, it has been necessary to combine two of the half-pound packages to make a marketable unit.

In an embodiment of the present invention, to be described hereinbelow in detail, means are provided to manufacture packages of increased depth and capacity, e.g. sufficient to hold ten frankfurters in a five-over-five relationship, thereby to obtain a significant reduction in the consumption of packaging materials. The present invention also provides packages having a better appearance, particularly by assuring improved conformity of the drawn face of the package (which is usually the display side) with the face of the product such as the top slice of a stack of luncheon meat. This result is achieved by minimizing the development of wrinkles in the transparent material lying against the product face, and by providing packages having smaller corner radii, so as to enhance the attractiveness of the package.

Accordingly, it is an object of this invention to provide improved packaging apparatus and methods for use in the 3,125,839 Patented Mar. 24., 1964 art of vacuum packaging. A more specific object of the invention is to produce packages of flexible packaging material having greater depth and interior capacity, as well as improved rectilinearity so as to permit packaging a maximum quantity of product in relation to the amount of packaged material utilized. A still further object of the invention is to provide packages having improved appearance and attractiveness. Other objects, aspects and advantages of the invention will be in part pointed out in, and in part apparent from, the following description considered together with the accompanying drawings, in which:

FIGURE 1 is a side elevation of a portion of the packaging machine;

FIGURE 2 is a horizontal section taken along line 2-2 of FIGURE 1 and showing the top of the vacuum manifold together with the frame and supporting cross pieces;

FIGURE 3 is a detail section taken along line 3--3 of FIGURE 2, showing the slide seal assembly in the initial stage of its engagement with the vacuum manifold;

FIGURE 4 is a detail section taken along line 44 of FIGURE 1, and showing the slide seal assembly positioned over the second port in the vacuum manifold;

FIGURE 5 is an enlarged detail section showing the gasketing arrangement of the slide seal assembly;

FIGURE 6 is a bottom view of the slide seal assembly taken along line 66 of FIGURE 3;

FIGURE 7 is a cross-section showing the manner in which the sheet separator is actuated for evacuation of the package; and

FIGURE 8 is a perspective view of the sheet separator.

Referring now to FIGURE 1, the packaging apparatus is basically similar to that disclosed in the above-mentioned copending application Ser. No. 842,365 wherein a large number of trays 10 are mounted on an endless chain (not shown herein) arranged to shift the trays horizontally with an intermittent indexing motion through a series of packaging stations identified as A, B, C, etc. Each tray includes a center partition 12 (see FIGURE 4) dividing the tray into two equal-sized side-by-side cavities in which the packages are formed. As explained in the aboveidentified copending application, a thin sheet of flexible plastic film 14 is unwound from a supply roll and applied across the top of each tray in succession as the tray moves into station A, the side edges of the film being clamped to the sides of the tray by a spring grip forming part of the tray (not shown herein). As the tray is indexed to station B, it comes under a radiant heater 16 which also extends over station C, and serves to soften the plastic film to prepare it to be stretched down into the cavities in the tray to form pockets into which the product is deposited.

The bottom of each tray 10 is provided with a slide seal assembly 18 which, as best shown in FIGURES 3 through 6, includes a movable seal element 20 defining an evacuation port 22 through which vacuum is applied to the interior of the tray. The seal element 20 is urged downwardly away from the tray by a coil spring 24, but its movement in this direction is limited by a retainer plate 26 bolted to the underside of the tray and formed with flanges 28 arranged to engage recessed shoulders 30 on the seal element. The retainer plate also is formed with an upstanding ring-shaped rim 32 around which is fitted a rubber gasket 34 having a U-shaped cross-section. This gasketing arrangement provides an air-tight connection to the seal element while permitting vertical or tilting movement of that element as will be described.

As the tray 11) is indexed from station B to station C, the seal element 20 engages the forked arms 36 (see also FIGURE 2) of a horizontal vacuum manifold 38. Arms 36 present an inclined surface which, as the tray is indexed to station C, gradually and smoothly shifts the seal element upwardly a small amount against spring 24, the tray itself being held against vertical movement by the usual side guide rails (not shown) adjacent the chain drive. Thus, when the tray ultimately is in position at station C, the seal element is clear of the retainer plate 26 and is spring-urged downwardly against the manifold 38 with suitable force so as to assure alignment with the surface of the manifold.

The seal element 20 is formed of a dimensionally stable low friction substance, such as graphite impregnated phenolic resin or nylon impregnated diallyl pthalate. The planar bottom face of this seal element is lapped flat and smooth, and the peripheral side surface also is accurately finished and dimensioned so as to engage the flange of the circular gasket 34 to prevent leakage of air. The upper surface of the vacuum manifold 38 is wider (laterally) than the seal element and engages the entire exposed surface thereof. The surface of the manifold is chrome plated and polished to a high degree of flatness and smoothness to assure an essentially airtight connection to the seal element.

Adjacent station C, the vacuum manifold 38 is provided with a vacuum port 40 similar in size and shape to the evacuation port 22 in the seal element 20, and aligned with the evacuation port when the tray is in station C. Vacuum is applied to port 40 through a fitting 42 connected to a conventional valve (not shown) which is operated by a cam drive in synchronism with the intermittent motion of the trays 1d. The vacuum connection to port 40 is equipped with a vacuum gauge 44, and a bleed-type regulating valve may also be connected at 46 if desired.

While the tray is stopped at station C, the heater 16 continues to soften the thin plastic film 14 which is clamped to the top of the tray. During this dwell time and just before the start of the next indexing movement, vacuum is applied through manifold port 46 and evacua tion port 22 to withdraw the air from the tray rapidly through a series of vertical holes 48 (four in each tray cavity) as well as through horizontal channels 56 which communicate with a chamber 52 having an opening in the bottom of the tray. Evacuation of the air from the tray draws the plastic film down into the tray cavities to form a pair of side-by-side package cups conforming generally to the tray outlines.

After the tray 10 starts to move from station C towards station D, but before ports 22 and 4 have become blanked ofl, the valve controlling the vacuum applied to fitting 42 is closed. Further movement of the tray causes both ports 22 and 40 to be blanked off simultaneously, the seal element 20 having a sufliciently large trailing edge (i.e. in the direction of movement) to prevent uncovering of port 40 until after port 22 has become completely blanked off.

At the end of this indexing cycle, when the tray 16 is at station D, the evacuation port 22 registers with a second port 54 in the vacuum manifold 38. This port 54 is connected through a pipe 56 to a continuous source of vacuum (not shown), preferably having a somewhat lower level than the vacuum source connected to the first manifold port 4t). The application of vacuum through port 54 renews and maintains the vacuum level within the tray cavities, so as to assure that the plastic film 14 is held in place against the interior tray surfaces. Thus there will be no significant spring-back or shrinkage of the plastic film, which particularly tends to occur as the plastic cools off after leaving the radiant heater 16. If desired, a bleed-type regulator valve $8 may be connected to the port 54 to control the vacuum level.

On the next indexing cycle of the machine, the tray 10 is moved to station E where the evacuation port 22 registers with a third manifold port all and the products to be packaged, e.g. frankfurters, are deposited in the tray cavities with the aid of a conveyor system 62. Port 64) is supplied with vacuum from the pipe 56 as is a fourth vacuum port 64 at station F. It will be evident that, as the tray is indexed between stations D, E and F, the vacuum is trapped within the tray cavities by engagement of the seal element 20 with the vacuum manifold 38, just as when the tray was shifted from station C to station D. The renewal of vacuum at each of stations, D, E, and F causes the plastic film to be urged towards the interior surfaces of the tray, thus helping to assure that the package will be wrinkle-free and have a maximum volume.

Each of the ports 54, 6t and 64- is provided with a corresponding orifice plug 66, 68 and 70, one of which (orifice 66) is shown in section in FIGURE 4. In one embodiment of the invention, these orifice plugs were identical except that orifice 66 had a slightly larger aperture /16") than the other two 0A3" each). By these means, precise control is exercised over the vacuum draw at stations D, E and F to further assure that there is essentially no slippage or flow of the film 14 from one tray to the next during packaging operations.

When the tray 10 is indexed beyond station F towards station G, the seal element 26 rides down the inclined arms '72 at the lefthand end of the vacuum manifold 33, and the evacuation port 22 thus is exposed to atmospheric pressure. By this time, however, the plastic film 14 has become sufficiently chilled that its tendency to shrink or spring back is greatly reduced. In addition, the weight of the product now in the tray cavities further tends to assure that the package depth remains at its maximum dimension, and that wrinkles are prevented so as to produce a superior package appearance.

From the above description, it will be evident that the invention described hereinabove provides a number of desirable features in vacuum packaging apparatus of the type wherein the package carriers move in a non-circular path, particularly by assuring that the plastic film is drawn down towards the bottom and sides of the tray cavities and is retained in this position due to the fact that vacuum is trapped in the trays while they are being indexed between stations C, D, E and F. As a result, there is no important shrinkage or spring back of the plastic film, and thus the volume of the package is maximized. Moreover, this arrangement minimizes slippage or flow of the film from one tray to the next during the indexing movement, as particularly can occur with machines wherein the package carriers move in a straight line, e.g. if the forming vacuum is applied during the dwell times but vented to atmosphere therebetween. Because of this feature, packages made by the disclosed apparatus have virtually no wrinkles and thus are attractive in appearance.

It should particularly be noted that the vacuum is trapped in the trays by means of a stationary member (i.e. the vacuum manifold 38) which extends between certain packaging stations and engages the slide seal assembly 18 during the indexing movement. This arrangement avoids the need for continuous vacuum connections to the trays as by means of cumbersome flexible hoses or the like travelling with the trays. Moreover, the invention is specially suited for use with a packaging machine wherein the package carriers move in a more or less straight path throughout at least a portion of their travel, i.e. not in a circular path as on the conventional drum, since it provides the desired results while permitting relative movement between the package carriers and the vacuum supply conduits to be connected thereto.

As explained in the above-identified copending application, Serial No. 842,365, beyond station G each tray 10 receives a second film of plastic packaging material which is sealed to the first film, and the complete package then is evacuated and/or gas-filled as desired. Referring now to FIGURES 7 and 8, as part of this package evacuation operation, the second film '74 is stretched up away from the first film by means of a sheet separator '76 slidably mounted in chamber 52 within the tray partition 12. The sheet-separator is operated by a mechanism which is located at a station beyond station H but beneath the packaging head 78. This mechanism includes a vertical pin 80 which is shiftable upwards by means of a pivoted arm 82 so as to push the sheet separator through the chamber 52, through a pre-formed aperture in the first film 14, and against the upper film 7 4 of packaging material.

Surrounding the pin St) is a gasket assembly 84 which also is moved up, by means of a second arm 86 springlinked to arm 82, so as to engage the seal element and thereby establish an air-tight channel from the top of the sheet separator 76 down to a supply conduit 88. While the separator 76 and gasket assembly 84 are in proper position, vacum is applied to the conduit 88 and the package is evacuated. Thereafter, the gasket assembly and the pin 80 drop down beneath the tray 10, and the sheet separator moves back down until its base rests against the spring snap ring 90 which is held captive in a groove extending around the bottom opening of the chamber 52. If it is desired to remove the sheet separator from the tray, this snap ring need only be rotated 45 and the sheet separator can be withdrawn.

Thus it will be evident that the described embodiment of the invention not only meets the desired objects of the invention by providing increased package capacity and improved appearance, but in addition is well adapted for the further packaging operations required to evacuate and/or gas-fill the completed package.

Although a preferred embodiment of the invention has been set forth in detail, it is desired to emphasize that this is not intended to be exhaustive or necessarily limitative; on the contrary, the showing herein is for the purpose of illustrating the invention and thus to enable others skilled in the art to adapt the invention in such ways as meet the requirements of particular applications, it being understood that various modifications may be made without departing from the scope of the invention as limited by the prior art.

We claim:

1. In packaging apparatus of the type wherein a number of package carriers are arranged to receive a film of packaging material to be stretched down by vacuum into a cavity in the carrier so as to form one surface of the final package, said package carriers being driven successively past a series of packaging stations, vacuum means at one of said stations for drawing said film down into the package carrier at that station, each of said carriers having a seal element defining an evacuation port to communicate with said vacuum means, means mounting said seal element for limited movement towards and away from its package carrier, resilient means urging said seal element in a direction away from its carrier, and sealing means extending from said one station to the next station to seal off the evacuation port in the carrier while the carrier is being moved from said one station to the next, said sealing means being positioned to engage said seal element and press it against said resilient means to establish an effectively air-tight connection therebetween.

2. In packaging apparatus of the type wherein a number of package carriers are arranged to receive in sequence a film of packaging material to be stretched down by vacuum into a cavity in the carrier so as to form one surface of the final package, said package carriers being driven successively past a series of packaging stations, vacuum means at one of said stations to provide suction for drawing said film down into the package carrier at that station, each of said carriers having a seal element having a smooth planar face on the side thereof opposite said carrier, said planar face being provided with an evacuation port to communicate with said vacuum means, means mounting said seal element for limited movement towards and away from its package carrier, resilient means urging said seal element in a direction way from its carrier, and a bar-like sealing means extending from said one station to the next station to seal off the evacuation port in the carrier being moved between said stations, said sealing means having a smooth planar surface engaging the planar surface of said seal element and urging said seal element against said resilient means to establish an effectively air-tight connection between said seal element and said sealing means.

3. Apparatus as claimed in claim 2, wherein said vacuum means includes a vacuum port located in the planar surface of said sealing means, said vacuum port being adapted to communicate with said evacuation port while the package carrier is at said one station.

4. Apparatus as claimed in claim 3, wherein said sealing means includes a second vacuum port adapted to communicate with said evacuation port when said carrier is at said next station.

5. In the art of making packages from flexible and stretchable packaging material, the method of vacuumforming the packaging material in the cavity of a package carrier comprising the steps of: applying the film across the top of the cavity; drawing the film down towards the interior surfaces of the cavity by evacuating the interior of the cavity with vacuum applied to an evacuation port while the package carrier is at a first operating station; trapping the vacuum in said cavity; moving said package carrier to a second operating station while maintaining the entrapment of the vacuum in the cavity so as to prevent any substantial movement of the film; reapplying vacuum to said evacuation port while said package carrier is in said second station; and depositing in said cavity a product to be packaged.

6. In the art of making packages from flexible and stretchable packaging material, the method of vacuumforming the packaging material in the cavity of a package carrier comprising the steps of: applying the film across the entrance opening of the cavity; evacuating the interior of the cavity by applying vacuum to an evacuation port While the package carrier is at a first operating station, thereby drawing the film down towards the interior surfaces of the cavity; trapping the vacuum in said cavity; moving said package carrier horizontally to a second operating station with the cavity opening facing upwards; maintaining said evacuation port sealed during the movement of said carrier, thereby to continue the entrapment of the vacuum in the cavity so as to prevent any significant movement of the film; reapplying vacuum to said evacuation port while said package carrier is in said second station; and depositing in said cavity opening a product to be packaged while the film is held stretched down towards the bottom of the cavity by vacuum.

7. In packaging apparatus of the type wherein a num ber of trays are arranged to receive a film of packaging material to be stretched by vacuum into a cavity in each tray so as to form a surface of the final package, said trays being driven in succession past a series of packaging stations, a slide seal assembly for each of said trays comprising a seal element mounted on the bottom of the tray and defining an evacuation port, retainer means accommodating limited movement of said seal element towards and away from said tray, a spring normally urging said seal element away from said tray and towards engagement with said retainer means, gasket means sur-.

rounding said seal element to provide an air-tight connection thereof to the bottom of said tray while permitting said limited movement, said tray being apertured to pro vide communication between said evacuation port and the interior of said cavity, and a vacuum manifold extending from one of said stations to a further station and provided with first and second vacuum ports which register with said evacuation port when a tray is in said one station and said further station respectively, said vacuum manifold including means to engage said seal element and seal off said evacuation port while the tray is being moved from said one station to said further station.

8. In packaging apparatus of the type wherein a number of trays are arranged to receive a film of packaging material to be stretched by vacuum into a cavity in the tray so as to form a surface of the final package, said trays being driven in succession past a series of packaging stations, a slide seal assembly for each of said trays comprising a seal element mounted on the bottom of the tray and defining an evacuation port, retainer means accommodating limited movement of said seal element towards and away from said tray, a spring urging said seal element away from said tray and into engagement with said retainer means, gasket means surrounding said seal element to provide an air-tight connection thereof to the bottom of said tray while permitting said limited movement, said tray being apertured to provide communication between said evacuation port and the interior of said cavity, and a vacuum manifold extending beneath at least three of said stations and provided with first, second and third vacuum ports which register with the evacuation ports of trays in said three stations, common vacuum means for supplying vacuum to said second and third ports, the orifice of said second port being slightly larger than the orifice of said third port, said vacuum manifold including means to engage said seal element and seal off said evacuation port while the tray is being moved from said one station to said further station.

9. In packaging apparatus of the type wherein a number of trays are arranged to receive a film of packaging material to be stretched by vacuum into a cavity in the tray so as to form a surface of the final package, said trays being driven in succession past a series of packaging stations, a slide seal assembly for each of said trays comprising a seal element mounted on the bottom of the tray and defining an evacuation port, retainer means accommodating limited movement of said seal element towards and away from said tray, a spring urging said seal element away from said tray and into engagement with said retainer means, gasket means surrounding said seal element to provide an air-tight connection thereof to the bottom of said tray while permitting said limited movement, said tray being apertured to provide communication between said evacuation port and the interior of said cavity, and a vacuum manifold extending from one of said stations to a further station and provided with first and second vacuum ports which register with said evacuation port when a tray is in said one station and said further station respectively, said vacuum manifold including means to engage said seal element and press it against said spring means to seal off said evacuation port while the tray is being moved from said one station to said further station, the approach end of said manifold being provided with a ramp-like member to provide gradual and smooth engagement with said seal element.

10. Apparatus :as claimed in claim 9, wherein said ramp-like member is formed with a pair of forked arms to engage only the side portions of said seal element.

11. Apparatus as claimed in claim 10, wherein the other end of said manifold also is provided with a ramp-like member formed with a corresponding pair of forked arms to assure gradual and smooth disengagement of said seal element as the trays are shifted to further operating stations.

12. Packaging appanatus comprising a plurality of trays linked end-to-end in a closed-loop chain-form configuration, said trays being interconnected to accommodate relative angular movement therebetween so as to permit the trays to be driven along a path having different radii of curvature at different points therealong, a section of said path extending past a series of consecutive packaging stations where various packaging operations are performed, each of said trays being adapted to receive a film of packaging material to be stretched down by vacuum into a cavity in the tnay so as to form a surface of the final package, a vacuum element defining a vacuum supply port at one of said stations and immediately adjacent said operating section of the path of movement of said trays, each of said trays having a seal element defining an evacuation port connected to the interior of its corresponding tray;

said seal element being positioned to slidably engage said vacuum element to establish communication between said evacuation port and said vacuum supply port when the corresponding tray is driven into operating position at said one station, thereby to provide vacuum to the tray for drawing said film down into the tray; one of said elements being mounted for limited movement towards and away from the other element to accommodate sealing engagement thereoetween, resilient means urging said one element towards said other element; said vacuum element including an elongated member having a sealing surface immediately adjacent said path section, said elongated member being disposed between said one station and the next station, said sealing surface being positioned to slidably engage each seal element as it is disengaged from said vacuum supply port when the tray is in transit to said next station, thereby to seal off the corresponding evacuation port while the tray is being shifted between said stations so as to hold the forming vacuum within the tray during this transition period.

13. Apparatus as claimed in claim 12, wherein one of said elements has an engagement surface which extends at a slight angle with respect to said section of the tray path, said engagement surface providing a smooth ramplike engagement between said two elements as the tray approaches said one station.

14. Packaging apparatus comprising a plurality of trays linked end-to-end in a closed-loop chain-form configuration, said trays being interconnected to accommodate relative angular movement between the trays so that the trays can be moved along a path having different radii of curvature at different points therealong, each of said trays being adapted to receive a film of packaging material to be stretched down by vacuum into a cavity in the tray so as to form a surface of the final package, means support ing said trays for movement in a generally oval path the plane of which is vertical, a portion of said path extending in a straight horizontal line past a series of consecutive packaging stations, said trays being disposed with the cavities thereof facing upwards as the trays move through said straight line path portion, vacuum means defining a vacuum supply port at one of said stations and immediately beneath said straight line portion of the path of movement of said trays, the open mouth of said supply port lying in a horizontal plane and facing upwards; each of said trays carrying a seal element which is approximately flush with the bottom surface of the tray, each of said seal elements defining an evacuation port the open mouth of which lies in a horizontal plane as the tray moves along said straight line path portion, said evacuation port being connected to the interior of its corresponding tray; said seal elements being positioned to slidably engage said vacuum means to establish communication between said evacuation port and said vacuum supply port when the corresponding tray is at said one station, thereby to provide vacuum to the tray for drawing said film down into the tray cavity; and tray sealing means comprising an elongated member having a sealing surface extending in a straight line immediately beneath and parallel to said straight line portion of the path of movement of said trays, said elongated member being disposed between said one station and the next station and contiguous with said vacuum means, said sealing surface being positioned to slidably engage each seal element as it is disengaged from said vacuum supply port when the tray is in transit to said next station, thereby to seal off the corresponding evacuation port while the tray is being shifted between said stations so as to hold the forming vacuum within the tray during this transition period.

15. Packaging apparatus comprising a plurality of trays linked end-to-end in a closed-loop chain-form configuration, said trays being interconnected to accommodate relative angular movement therebetween so as to permit the trays to be driven along a path having different radii of curvature at different points therealong, a section of the 9 tray path extending past a series of consecutive packaging stations where various packaging operations are performed, each of said trays being adapted to receive a film of packaging material to be stretched down by vacuum into a cavity in the tray so as to form a surface of the final package, a vacuum element defining a vacuum supply port at one of said stations and immediately adjacent said operation section of the path of movement of said trays, each of said trays having a seal element defining an evacuation port connected to the interior of its corresponding tray, said seal elements being secured to the corresponding tray for movement therewith along said path, said seal elements being independently mounted for angular movement relative to one another as the trays are driven about said path, each of said seal elements being positioned to slidably engage said vacuum element to establish communication between said evacuation port and said vacuum supply port when the corresponding tray is driven into operating position at said one station, thereby to provide vacuum to the tray for drawing said film down into the tray; and tray sealing means comprising an elon ated member having a sealing surface extending alongside said section of the path of tray movement, said elongated member being disposed between said one station and the next station and contiguous with said vacuum element, said sealing surface being positioned to slidably engage each seal element as it is disengaged from said vacuum supply port when the tray is in transit to said next station, thereby to seal off the corresponding evacuation port while the tray is being shifted between said stations so as to hold the forming vacuum within the tray during this transition period.

16. Apparatus as claimed in claim 15, wherein each of said seal elements is supported solely by its corresponding tray, the open mouth of the evacuation port defined by each seal element being closely adjacent the outer surface of the corresponding tray.

17. Packaging apparatus of the type having a number of trays mounted end-to-end in a closed-loop configuration, eaoh of said trays being adapted to receive a fihn of packaging material to be stretched down by vacuum into a cavity in the tray so as to form a surface of the final package, means supporting said trays for movement past a series of consecutive packaging stations, firs-t vacuum means defining a first vacuum supply port at one of said stations, a seal element for each tray and defining an evacuation port connected to the interior of its corresponding tray, said seal element being positioned to slidably engage said first vacuum means to establish communication between said evacuation port and said first vacuum supply port when the corresponding tray is at said one station, thereby to provide vacuum to the tray for drawing said film down into the tray cavity, tray sealing means comprising a member having a sealing surface extending from said one station to the next station and contiguous with said first vacuum means, said sealing surface being positioned to slidably engage each seal element as it is disengaged from said vacuum supply port when the tray is in transit to said next station and to seal off the corresponding evacuation port while the tray is being shifted between said stations so as to hold the forming vacuum within the tray during this transition period, and second vacuum means contiguous with said sealing means surface and defining a second vacuum supply port at said next station, said second vacuum means being positioned to engage each seal element as the corresponding tray reaches said next station and to establish communication between said evacuation port and said second vacuum supply port to reapply vacuum to said tray while at said next station.

18. Packaging apparatus comprising a plurality of trays linked end-to-end in a closed-loop chain-form configuration, said trays being interconnected to accommodate relative angular movement therebetween so as to permit the trays to be driven along a path having different radii of curvature at different points therealong, a section of the tray path extending past a series of consecutive packaging stations where various packaging operations are performed, each of said trays being adapted to receive a film of packaging material to be stretched down by vacuum into a cavity in the tray so as to form a surface of the final package, a vacuum member defining a vacuum supply port at one of said stations and immediately adjacent said section of the path of movement of said trays, each of said trays carrying seal means including a seal element defining an evacuation port connected to the interior of its corresponding tray; said seal element comprising a lip member around the open mouth of said evacuation port, said lip member having a smooth slidable surface at the end thereof defining said open month; each of said seal elements being separate from and mounted for independent angular movement with respect to the other seal elements; each seal element being positioned to slidably engage its smooth end surface with said member to establish communication between said evacuation port and said vacuum supply port when the corresponding tray is driven into operating position at said one station, thereby to provide vacuum to the tray for drawing said film down into the tray, said vacuum member including an elongated member having a sealing surface extending alongside said section of the path of tray movement, said elongated member being disposed between said one station and the next station, said sealing surface being positioned to slidably engage the smooth end surface of each seal element as it is disengaged from said vacuum supply port when the tray is in transit to said next station, thereby to seal oh? the corresponding evacuation port while the tray is being shifted between said stations so as to hold the forming vacuum within the tray during this transition period.

19. Apparatus as claimed in claim 18, wherein the trailing edge of said lip member has a dimension, in the direction of movement of said trays, which is sufiiciently long to prevent uncovering of said supply port until after said evacuation port has become completely blanked ofl? while the tray is moving from said one station to said next station.

References Cited in the file of this patent UNITED STATES PATENTS 2,935,828 Mahaffy et al May 10, 1960 

5. IN THE ART OF MAKING PACKAGES FROM FLEXIBLE AND STRETCHABLE PACKAGING MATERIAL, THE METHOD VACUUMFORMING THE PACKAGING MATERIAL IN THE CAVIT OF A PACKAGE CARRIER COMPRISING THE STEPS OF: APPLYING THE FILM ACROSS THE TOP OF THE CAVITY: DRAWING THE FILM DOWN TOWARDS THE INTERIOR SURFACE OF THE CAVITY BY EVACUATING THE INTERIOR OF THE CAVITY WITH VACUUM APPLIED TO AN EVACULATION PORT WHILE THE PACKAGE CARRIER IS AT A FIRST OPERATING STATION; TRAPPING THE VACUUM IN THE CAVITY SO AS TO PREVENT ANY SUBSTANTIAL MOVEMENT OF THE FILM; REAPPLYING VACUUM TO SAID EVACUATION PORT WHILE SAID PACKAGE CARRIER IS IN SAID SECOND STATION; AND DEPOSITING IN SAID CAVITY A PRODUCT TO BE PACKAGED. 